


Sooner or Later

by dracoqueen22



Category: Transformers - All Media Types
Genre: M/M, Spark Sexual Interfacing (Transformers), Sticky Sexual Interfacing, Technically Illegal Incest, Twincest
Language: English
Status: Completed
Published: 2020-10-26
Updated: 2020-10-26
Packaged: 2021-03-09 02:35:13
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,057
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27196571
Author URL: https://archiveofourown.org/users/dracoqueen22/pseuds/dracoqueen22
Summary: [Sequel to Shatter Me] An offhand comment from Swindle has Sideswipe reconsidering – and remembering – the decision to claim Sunstreaker as his.
Relationships: Sunstreaker/Sideswipe
Comments: 8
Kudos: 59





	Sooner or Later

**Author's Note:**

  * For [fuzipenguin](https://archiveofourown.org/users/fuzipenguin/gifts).
  * Inspired by [Shatter Me](https://archiveofourown.org/works/6848317) by [dracoqueen22](https://archiveofourown.org/users/dracoqueen22/pseuds/dracoqueen22). 



“Word on the street is that you two haven’t been seen in the clubs for a month.”  
  
Sideswipe side-eyed Swindle as he double-checked the manifest against the items in the order. Sunstreaker would murder him if Swindle left anything out again.  
  
“We’ve been busy,” Sideswipe said.  
  
Swindle grinned that shark-grin Sideswipe hated. “So busy you couldn’t possibly find a frag for the night? I don’t believe it.” He tilted his head, the curl of his lips predatory. “What’s his designation, eh? Don’t tell me you finally settled for someone.”  
  
"Who has time for a permanent partner?" Sideswipe snorted. He checked the last item before signing off on the manifest and holding it out. "Congratulations on not trying to frag us over this time."  
  
Swindle held a hand to his chassis in mock offense. "Me? I would never." He plucked the datapad from Sideswipe's hand. "Besides, who's the one being deceitful here?"  
  
"Because I don't want to discuss the specifics of my 'facing life?" Sideswipe rolled his optics and picked up the crate, tucking it down behind the counter and out of Swindle's reach. Stuff had vanished from the crate after he checked it before.  
  
"Can't blame a curious mech for asking." Swindle shrugged as the datapad vanished into subspace. "Two pieces of shareware suddenly stop sharing? The rumor mill is abuzz." He grinned and leaned on the counter, into Sideswipe's space. "Mechs start wondering if you got something to hide."  
  
Sideswipe barked out a laugh. "We're all hiding something, Swin. It's why we live here." He made a vague gesture to the city beyond the shop. "Don't you have other deliveries to make?"  
  
Swindle patted his hands on the counter before pushing back from it. "True. And it does pay to be punctual." He winked at Sideswipe. "I'll save this mystery for next time."  
  
"Can't wait," Sideswipe drawled.  
  
Swindle sailed out the door, which chimed brightly at him, and Sideswipe didn't ventilate until the oily mech was gone. Only then did he shutter his optics, brace his hands on the edge of the counter, and let the worry unfurl in his spark.  
  
Mechs were asking questions, hm? He supposed it made sense. He and Sunstreaker had been very socially active up until a month ago. They took a new mech home every week it seemed, sometimes to share, sometimes singly depending on their moods. They had a bit of a reputation, well-earned as it was.  
  
Sideswipe doubted anyone would leap to the conclusion that he and Sunstreaker were fragging each other, but given enough time, enough doubt, enough suspicion...  
  
As much as they fragged others, they had a reputation for being insular and never keeping partners past the one night. They didn't date. They had no serious relationships.  
  
Sometimes, suspicion was all one needed.  
  
Swindle was proof enough.  
  
Sideswipe vented a sigh and lifted the crate of supplies back onto the counter, distributing the contents where they belonged. It wasn't something that required much thought, luckily, since his attention was now elsewhere. Elsewhen. Specifically, a month ago, when he and Sunstreaker had shared a local mech, and realized, what they really wanted was to frag each other.  
  
Well.  
  
Sunstreaker had finally figured it out.  
  
Sideswipe had known for years.  
  
He wasn't sure when it started, when he first looked at Sunstreaker and wondered how his brother would taste or feel, or when he became jealous of their interface partners because he wanted to be the one making Sunstreaker overload. It started gradually, he was sure. Bit by bit, until it became this thing he had to hide in the deepest recesses of his spark.  
  
It was wrong. He was disgusting for even thinking of it. Sideswipe told himself this time and time again. He loved Sunstreaker, he loved his twin. He'd never do anything to hurt Sunstreaker, and so, he'd kept those dark desires to himself. He didn't want to become a monster.  
  
It wasn't until that night with Hound, when Sunstreaker looked at him, and for the first time, Sideswipe saw desire reflected in his optics. Not for their berthpartner. No, Sunstreaker had already dismissed Hound. It was a hunger for Sideswipe.  
  
He thought his spark would explode with happiness. They came together naturally, and it was so easy between them, so easy to kiss Sunstreaker and touch him and be the cause of the pleasure spiralling out of Sunstreaker's field. He’d been beside himself when he realized the volcanic need in Sunstreaker’s field was for _him_. Not Hound, but _him_. Sideswipe.  
  
Sunstreaker had sank into the kiss as though he’d been waiting for it all his life. He trembled in Sideswipe’s arms, his field pulsing need-want-more-please, and Sideswipe had been helpless to it, helpless to what Sunstreaker wanted, and the dam broke, the door cracking open to release a torrent of pent-up need.  
  
Sideswipe had been as ecstatic as he'd been guilty. It was only later, when Sunstreaker was recharging half on top of him, that the reality of what they'd done had hit him. They should have talked first. He felt more than a little like he'd taken advantage of Sunstreaker.  
  
After all, Sideswipe had been the first to harbor these monstrous thoughts. Had he infected Sunstreaker somehow? Had he seen a moment of weakness and used it to his advantage?  
  
The guilt clogged Sideswipe's intake.  
  
It would only be the once, he’d told himself, in that moment and over the long-long night where he slept in fitful bursts of choking guilt. In the morning, they’d talk, and Sunstreaker would realize he’d made an enormous mistake. Sideswipe would tuck his monstrous wants back into the vault where they belonged, spending the rest of his life making it up to Sunstreaker. His twin. Spark of his spark.  
  
At least, that was the plan.  
  
Because the next morning Sunstreaker onlined, snuggling into Sideswipe’s intake with a little contented hum, and rasped ‘good morning’. Sideswipe’s resolve cracked, and then it crumbled when Sunstreaker leaned up, brushed a kiss over his lips, and offered the shyest, sweetest smile in the aftermath.  
  
It was the smile which had undone him.  
  
Sideswipe kissed him again, because there was no power in the universe that could have stopped him in the moment, unless Sunstreaker said so. Sunstreaker melted into the kiss, melted into him, and their interfacing that morning could only be called ‘lovemaking’.  
  
Sideswipe sighed as he stowed the last of the supplies and slid the crate back under the counter. He’d exchange it with Swindle at the next delivery. His spark wasn’t in running the shop right now, so Sideswipe closed up early, locked the doors, and flicked off the lights. He’d open early tomorrow to make up for it.  
  
He really should try and contact Hound, come to think of it. Apologize, at the very least, for having him depart so abruptly. Thank him, too. Not that Sideswipe could really explain what he was thanking the mech for.  
  
Hmm.  
  
Problem for another time.  
  
Sideswipe locked the creds drawer into the safe, drew the security blinds, and doused the open sign. He’d worry about cleaning tomorrow. Right now, he needed to talk to Sunstreaker.  
  
Off into the back he went, where Sunstreaker was hard at work on some projects, or at least, intended to be hard at work. Sometimes, it didn’t work out. Sideswipe didn’t presume to know what that meant. He wasn’t as creative as his twin.  
  
At least, not when it came to art. Sideswipe’s creativity emerged in different ways.  
  
He had to tell Sunstreaker about Swindle. It was probably nothing, but it did point to a potential future problem. Sideswipe couldn’t decide what to do on his own. He’d need Sunstreaker’s input, too.  
  
Soft music drifted out of the workroom -- no lyrics, just a gentle spill of delicate chimes and electrobass -- and beneath it, the sound of Sunstreaker grumbling. Sideswipe paused in the doorway, affection seizing his spark, as Sunstreaker stood over his array of paints, clearly rearranging them. There were a few splotches of color on his canvas, but Sideswipe had been around long enough to realize they weren’t the precursors of a finished piece, but the exasperated swipe of an uninspired brush.  
  
“No luck today?” Sideswipe asked as he flopped down in the comfy chair Sunstreaker kept just for him. It was the only piece of furniture in the room not covered by art supplies or half-finished canvases.  
  
Sunstreaker snorted and glanced over his shoulder. “Shouldn’t you be watching the shop?”  
  
“Closed early.” Sideswipe rested his chin on his knuckles. “Swindle brought by your supplies.”  
  
“Did you--”  
  
“Check them against the manifest? Of course I did.” Sideswipe grinned at his twin, giving his most winsome smile, before it faded. “He mentioned something though.”  
  
The armor at Sunstreaker’s shoulders tightened. “That doesn’t sound good.”  
  
“That depends on how you look at it.” Sideswipe rubbed his hands around his mouth and sucked in a vent. “Mechs are talking, Sunny. Seems they noticed we don’t go hunting for a frag anymore.”  
  
Sunstreaker very slowly and deliberately placed a shade of red between two other shades of red whose differences were so miniscule Sideswipe couldn’t tell them apart. “So? Maybe we just got bored of that.”  
  
“Sure,” Sideswipe said with a shrug. “They’d believe that of you, maybe.” He cycled a vent as Sunstreaker’s shoulders grew more and more tense. “Course, no one’s drawing a line to… to what we’re actually doing. But suspicion, you know. People start talking, start theorizing, who knows…”  
  
Sunstreaker swapped the positions of two shades of red. “Theorizing that we’re fragging each other, you mean,” he said, tone tight.  
  
Sideswipe flinched. “That’s not what I think of it as, but yeah. It only takes one, Sunny.”  
  
“Mm.” Sunstreaker’s noncommittal reply did more to reveal his emotional state than actual words. “You always have a plan, right? So what’s your plan?”  
  
“Plan?” Sideswipe gnawed on his bottom lip, spark quivering into knots of anxiety. “Best way to squash rumors is to get back up to our old tricks, right? Maybe not as often as we did before, but enough people find something better to gossip about.”  
  
Sunstreaker rested his hands on the edge of the paint case. “You want to frag other mechs?”  
  
“Not because I want to, but because it’s a good cover.” Sideswipe watched Sunstreaker carefully, but Sunny’s half of the bond was muffled to him, and there were little hitches in Sunstreaker’s vents which suggested he was trying to hold back. “We’ll have each other no matter what, Sunny.”  
  
Sunstreaker looked at him finally, though it was askance and guarded. “Maybe it’s a sign. If we have to hide it, we shouldn’t be doing it.”  
  
Frag.  
  
This was what Sideswipe worried about. He shoved all of the emotions down deep, guarding them from Sunstreaker. He knew what he wanted, but he refused to push Sunny into anything. As long as he had Sunstreaker, he didn’t care how their relationship was defined.  
  
“Do you want to stop?” Sideswipe asked, proud of himself for keeping his tone light and curious, rather than hurt and accusatory.  
  
Sunstreaker tilted his head. “Shouldn’t we?”  
  
Sideswipe’s spark lurched. “Why?” he asked. “Because a bunch of strangers don’t approve?”  
  
“It has to be illegal for a reason, Sides,” Sunstreaker said in an exasperated tone. He finally turned to look at Sideswipe fully, and the indecision was written across his face.  
  
“Since when have we cared about what’s legal?” Sideswipe wasn’t panicking. He was choosing his words carefully and deliberately, and absolutely not panicking. “Or what other people think?”  
  
Sunstreaker folded his arms across his chassis, shoulders hunching. “This is different,” he said, and he stared at the floor, forehead scrunched.  
  
Damn it.  
  
Sideswipe cycled a ventilation and stood. Some things were more important. “Do you want to stop?” he asked, and kept his side of the bond locked down tight. “If you don’t want to interface with me, I’ll never touch you again. But is it because you think you ought to, or because you actually want to?”  
  
Sunstreaker didn’t immediately answer. His shoulders hunched up to his audials, his vents audibly ragged. His field, what Sideswipe could sense of it, was chaotic and confused.  
  
Sideswipe moved closer, his spark aching. He’d done this. He’d been the one to cause this pain in his twin. Truly, he was the monster here. And yet.  
  
And yet, he had to know.  
  
“I don’t care what anyone else thinks,” Sideswipe murmured. The burden shouldn’t be Sunstreaker’s alone, after all. “We’re both adults, and were when we started this. We’re not hurting anyone. So I don’t care, and I don’t regret it.”  
  
Sunstreaker’s intake bobbed. “What you don’t care about isn’t the same as everyone else. It’s not going to stop them from arresting us.”  
  
“And charge us with what?” Sideswipe asked.  
  
Sunstreaker threw his hands into the air, optics flickering, wild. “I don’t know,” he spluttered. “Crimes against Primus’ law? Do I look like a lawyer?”  
  
Sideswipe captured Sunstreaker’s hands, alarmed to find them shaking, and gently rubbed his thumb over Sunstreaker’s palms. “I’ve already looked into it,” he said. “Legally, we’re adults, and we’re our own guardians. They can’t arrest us. There’s nothing to charge us with.”  
  
Sunstreaker pressed his lips together in a line before saying, “I’m sensing a ‘but’.”  
  
Damn.  
  
He was too smart for his own good sometimes.  
  
Sideswipe sighed and concentrated on Sunstreaker’s fingers curled against his. “They could take away our business license and evict us from the apartment, if they wanted.”  
  
An icy shiver raced through Sunstreaker’s field, a spike of fear and unease, and Sideswipe tightened his grip on Sunstreaker’s hand, trying to pulse reassurance and comfort from his field.  
  
“None of that matters though,” Sideswipe said, desperately. “There are places we can go that no one would care. Like… like Kaon or Tarn or whatever. Somewhere they don’t know us!”  
  
Sunstreaker’s ventilations hitched. “And start over? Leave everything behind? We worked hard to get this stuff, Sides!”  
  
Yes, they had.  
  
They’d scrimped and saved and worked jobs they hated, and did things they despised, and fought fang and talon to carve out this little space for each other.  
  
But.  
  
Sideswipe drew in a long vent and cupped Sunstreaker’s face, thumb a soft sweep over his cheek. “Stuff is stuff. Everything I need is you,” he murmured. “As long as I’m with you, I don’t care about the rest.”  
  
He’d loved Sunstreaker for longer than he could remember. He loved him before they started fragging each other, and he’d love Sunstreaker even if they stopped. Sunstreaker was his brother, his twin, the other half of his spark. Sideswipe would be nothing without him and that was the truth.  
  
As long as he had Sunstreaker, he didn’t need anything or anyone else.  
  
“I love you,” Sideswipe said as Sunstreaker’s silence lingered, but his face went through a flurry of emotions. “I would fight Primus himself to be with you, but if that’s not what you want, we can go back to the way things were.”  
  
It was a painful thought, now that he knew how Sunstreaker tasted and how he moaned, and how he reacted to Sideswipe’s touch, but he’d still do it. He’d rather lose that than Sunstreaker. It’s not about the interfacing. Not really. It’s about being with Sunstreaker, being close to him, and never losing him.  
  
Sunstreaker shuttered his optics. “I love you, too,” he whispered, and a shudder ripped across his armor, wafting tension and worry in radiating waves. “And I don’t want to go back.”  
  
Hope welled within him, and Sideswipe swallowed it down. “Are you saying that for me or because it’s what you really want?”  
  
Sunstreaker looked up at him with a scowl. “Since when do I ever give in to what you want?” he demanded.  
  
“Often enough I know to be suspicious.” Sunstreaker was a gentle spark, for all his surly exterior. He would never bring himself to hurt Sideswipe, and vice versa.  
  
Sunstreaker set his jaw. “Look in my spark then.”  
  
Beneath Sideswipe’s palm, Sunstreaker’s armor parted, enough that the buzzing warmth of his spark peeked through, promising and offering so much. Sideswipe’s own jittered in response, his knees a little wobbly. Sunstreaker caught him with a strength no one would expect of an artist, and sank back, pulling Sideswipe with him, toward a paint-spattered chair.  
  
Sideswipe landed in Sunstreaker’s lap with less grace than he usually displayed, but that didn’t matter, because it was where he wanted to be.  
  
He cupped Sunstreaker’s face, thumbs sweeping over his cheeks, and pressed their foreheads together. “It’s okay if you say no,” Sideswipe whispered as his spark sensed Sunstreaker’s nearby and surged forward, desperate to reunite with its better half.  
  
“I know,” Sunstreaker said, oddly gentle as he pulled Sideswipe closer, notching their frames together, chest to chest, the heat of his spark eager against the slight crack in Sideswipe’s chassis. “Open for me, Sides.”  
  
He wanted to kiss Sunstreaker so badly, but he didn’t. Not until he was sure Sunstreaker wanted the same thing.  
  
“Anything for you,” Sideswipe murmured as he obeyed and stopped fighting the pull of his spark.  
  
His chestplate parted, spark energies immediately leaping out, seeking contact with Sunstreaker’s own. The glow lit between them, bright and beautiful, and between one vent and the next, their exterior coronae collided.  
  
_Love_.  
  
Overwhelmingly, love was the first thing which swept through the merge. Distantly, his frame twitched and shuddered with inevitable pleasure, the breadth and weight of Sunstreaker’s love swallowed him. It suffused every beat of Sunstreaker’s spark, and Sideswipe ached at the feel of it. He pulsed it back in kind, bundling up all the little moments where he’d fallen deeper and deeper for his twin, and felt the puff of Sunstreaker’s gasp against his cheek.  
  
Sunstreaker inched closer, tangling their secondary coronae together, and Sideswipe groaned, shivering as heat followed in the wake of the love. Glimpses of Sunstreaker’s desire for him flashed through the merge -- himself through Sunstreaker’s optics, the things Sunstreaker had imagined or fantasized, snippets of their prior interfacing.  
  
_More._  
  
Sunstreaker wanted so much more. The desire he felt matched Sideswipe’s own, almost suffocating for its strength, and the honesty of it unlocked what Sideswipe had been taking care to hide. He flung open the door, returning Sunstreaker’s desire in kind, admitting for the first time how very long he’d wanted Sunstreaker.  
  
Metal creaked. Sunstreaker pressed against him harder, as if trying to meld their physical bodies together as much as their sparks. He honest to Primus whimpered, which sent a shock of need straight to Sideswipe’s array.  
  
Sunstreaker _wanted_ him.  
  
He honestly _wanted_ this.  
  
Joy lit Sideswipe’s sensor net in a flood of crackling heat. He tightened his grip on Sunstreaker’s face and dragged his mouth to his twin’s, kissing Sunstreaker like a starving mech, and groaned when Sunstreaker kissed him with equal fervor, glossa plunging into his mouth, and denta scraping his lips.  
  
One pulse. Two pulses. Three. Arrhythmic at first, until the separated halves of their spark remembered how they were supposed to beat, and Sideswipe swore the moment their sparks synced, his universe clicked into place. All doubts and regrets vanished, and maybe it was wrong in the optics of everyone else, but nothing ever felt as right as this moment -- Sunstreaker kissing him, and their sparks merged as one.  
  
It couldn’t last.  
  
There’s a reason they were twins. There’s a reason their sparks split. Instability crackled around the edges of their combined cores, pleasurable at first, but the more it resisted, Sideswipe knew it would start to hurt. He didn’t want to disentangle from Sunstreaker. He wanted to bathe in this pure love and desire for the rest of his life.  
  
Their sparks pulled apart, tendrils unwinding and snapping, retreating back to the safety of their own chambers. Sideswipe shivered in the aftermath, struggling with the lingering sensation of abandonment. It was hard not to feel bereft when he was no longer merging with Sunstreaker. Sometimes, he hated being stuck in his own frame.  
  
But then Sunstreaker kissed him again, glossa plunging into his mouth, hands on his hips, yanking Sideswipe against him, rocking up and--  
  
Whoa.  
  
That was Sunstreaker’s spike, hot and wet, grinding against Sideswipe’s inner thigh, painting pre-slick over his closed panel.  
  
“Please,” Sunstreaker groaned against his mouth, his optics unshuttered, burning bright and hungry and rippling with love. “Let me in, Sides,” he pleaded and rocked up again, his spike scrubbing over Sideswipe’s array cover.  
  
Lust throbbed so quickly through Sideswipe’s frame he felt dizzy with it. Sunstreaker’s field was full of it -- hot and sticky -- and he peppered Sideswipe’s jaw with kisses and little bites. His fingers explored seams as he shifted and rocked beneath Sideswipe, clearly eager for it.  
  
“Yes,” Sideswipe moaned, and slung his arms over Sunstreaker’s shoulders, digging his feet into the floor. He canted his hips, and his panel snicked aside a mere blink before he sank down on Sunstreaker’s spike. His valve sang with pleasure.  
  
He kissed Sunstreaker, again and again, as Sunstreaker rocked up into him, deep strokes that licked fire over his internal nodes. His spike scrubbed against Sunstreaker’s abdomen, leaving streaks of pre-spill behind, but Sunstreaker didn’t complain. He kept kissing Sideswipe, kept nibbling along his jaw, licking and sucking at his intake, his hands roaming like he didn’t dare stop touching.  
  
Sunstreaker’s spike was rigid, pulsing, as if he’d been on the edge of overload throughout the entire merge. Sideswipe realized that he’d been much the same, the sensation distant until he returned to his frame. The need was there now -- raw and volcanic -- so he rode Sunstreaker’s spike, rutted up against his belly, pressed their chassis together until he could feel the echo of Sunstreaker’s sparkpulse.  
  
Love, love, love was the rhythm of Sunstreaker’s spark, and Sideswipe knew his own was the same. Better still was the desire -- Sunstreaker kissing him like Sideswipe was the only thing he needed, Sunstreaker’s spike pulsing charge over his valve nodes until they sang, Sunstreaker’s hands mapping every plane of his armor.  
  
Overload struck like a bolt of lightning, and Sideswipe pressed his forehead to Sunstreaker’s clavicular strut, shaking as he spilled against Sunstreaker’s abdomen, and his valve spiraled tight. Sunstreaker’s gasp puffed over his audial, fingers gripping his hips tight, as he bucked up sharply. Sideswipe groaned, pleasure dancing behind his optics, when the hot splash of Sunstreaker’s transfluid painted his valve, sending him into a second, smaller overload.  
  
He panted, dragging his mouth back to Sunstreaker’s, into a kiss hot and sloppy, need still yawing inside of him. It was Sunstreaker’s turn to cup his face, to keep him close for each subsequent kiss, deep and slow and savoring.  
  
“Love you,” Sunstreaker murmured. “Want you.” He mouthed along the curve of Sideswipe’s jaw. “Believe me?”  
  
Sideswipe hummed and pressed his forehead to Sunstreaker’s. “Always,” he murmured as he shifted, but Sunstreaker was yet firm inside of him. “Spark of my spark.”  
  
Sunstreaker breathed a helpless laugh, and joy lit through his field like a blooming firework. He stroked Sideswipe’s cheek, soft and worshipping. “My better half,” he said. “Did you completely close up the shop?”  
  
“Of course I did.”  
  
Sunstreaker shifted beneath him, the tiniest thrust, and Sideswipe shivered. “Come to berth with me?”  
  
“What about your sorting?” Sideswipe teased as he nipped at the edge of Sunstreaker’s head-fin where he was most sensitive.  
  
“It can wait.” Sunstreaker nuzzled into his intake, pressing kisses along his cabling. “I don’t want to frag anyone else, Sides. But if that’s what we have to do…”  
  
Sideswipe’s spark clenched. He leaned back and tucked a knuckle under Sunstreaker’s chin, tipping his head up. “You don’t want to, then we won’t, that’s all there is to it,” he murmured. “If something happens, we’ll deal with it then.”  
  
“You’re the one who’s always plotting things,” Sunstreaker pointed out. “Make a plan for this, too.”  
  
Sideswipe tipped their foreheads together. “I don’t want anyone but you either. I’ll take care of it.”  
  
“Good.” Sunstreaker smiled again, soft and shy and radiant, and Sideswipe fell in love with him all over again. “Come to berth with me now?”  
  
“Ask me something hard,” Sideswipe murmured. He could worry about the rest later.  
  
There was nowhere else Sideswipe would rather be.  
  


***

**Author's Note:**

> Feedback, as always, is welcome and appreciated.


End file.
